Hi Fil, welcome to CS!
I have one of these (my old machine) and there are a heap of things that could be attributing to the problems with your shots.
1. Stale coffee (once ground it is stale within 3 mins). So start saving for a grinder... *;)
2. The pressurised baskets that come with your machine produce fake "crema" and are designed for stale supermarket coffee. Many lower end sunbeam users replace these with Krups non-pressurised baskets (you must freshly grind to use these).
3. Underdosing. The recommended method is to overfill the basket lightly tamp, top up to a heap again then tamp.
4. The grind is too coarse which is leading to under extraction.
5. Tamper. If you are using the supplied plastic thing you wont be tamping hard enough no matter what you do.
This is just to mention a few! Other CSs will surely respond soon with more advice.
BTW these are things that have worked for me if im wrong however im sure the experts around here will correct me... *My EM4800C can consistently pull a double shot of 60ml in 25 seconds (give or take a ml/sec or two).
Now that you have discovered CS the bug will surely bite.
Best of luck *:)